ok, next trial..
in mybb16_to_smf.sql
find:
SUBSTRING(IF(p.edituid > 0, edit_u.username, ''), 1, 255) AS modified_name,replace with:
SUBSTRING(IF(p.edituid > 0, edit_u.username, 0), 1, 255) AS modified_name,this solution is far away from perfect but it should work and we could fix it later with a simple SQL statement
UPDATE smf_messages SET modified_name = '' WHERE modified_name = 0;